3 Describe the conditions of maximum output for an electric arc furnace.

4. Describe the working principle of outrasonic welding for joining of plastic materials.

5. Explain the operations of the following with circuit diagrams :

a ) LP sodium vapour lamp b ) LP mercury vapour lamp

6. Write short notes oi> any one of the following :

a) Resistance heating

b) Induction heating

c) Dielectric heating.

GROUP -C ( Long Answer Type Questions )

Answer any three of the following. 3 x 15 = 45

7. a) Explain the factors to be taken into account for designing schemes for (i) street lighting (ii) flood lighting.

b) What are the advantages of using coiled coil filaments in tungsten filament lamps ?

c) State and explain LOR.

d) Estimate the number and wattage of lamps which would be required to illuminate a workshop space 60 m x 15 m by means of lamps mounted 5 m above the working plane. The average illumination required is about 100 lux, coefficient of utilization = 0.4, luminous efficacy = 16 lumen per watt. Assume a space-height ratio ol unity and candle power depreciation of 20%.

8. State the advantages of electric heating. Explain the principle of induction heating. What are the applications of induction heating ? What are dielectric heating and dielectric loss ?

A low frequency induction furnace operating at 10 volts in the secondary circuit takes 500 kW at 0-5 p.f. when the hearth is full. If the secondary voltage be maintained at 10

volts, estimate the power absorbed and the power factor

when the hearth is half-full. Assume the resistance of the secondary circuit to be thereby doubled and reactance to remain same.

9. a) Explain how rheostatic braking is employed to a d.c.

series motor when at least two motors are working ir parallel for electric traction system.

b) Define tractive effort for acceleration and for overcoming the effect of gravity for propulsion of the train.